Using message-passing with procedural code in a database kernel

ABSTRACT

Each of a plurality of database objects can be assigned to a specific message-passing worker of a plurality of message-passing workers, each executing on a first logical core that shares with at least a second logical core one or more resources of a physical processor core of a plurality of physical processor cores. The second logical core can execute a job worker of a plurality of job workers that implement procedural code. Exclusive write access can be provided to a database object of the plurality of database objects via a message-passing worker of the plurality of message-passing workers while read-only access is provided to any database object of the plurality of database objects via any of the plurality of job workers. Operations can be executed by the message-passing worker in an order in which request messages are received in a message queue of the message-passing worker.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/062,810, filed on Oct. 24, 2013, and entitled “Using Message-Passingwith Procedural Code in a Database Kernel”, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The subject matter described herein relates to computing and processingoperations, for example computing and processing operations relating todatabase management frameworks.

BACKGROUND

Access to shared data structures, for example in a database managementsystem, can generally be implemented either through locking ormessage-passing. In a locking approach, exclusive access to shared datais given to a thread that is currently acting on the data structure.Other threads needing access to that data structure are required towait.

Many currently available software programs are written and optimized forexecution on a single central processing unit (CPU) or perhaps more thanone but relatively few CPU physical cores in a procedural approach thatincludes synchronization via locks and deep call stacks. Proceduralprogramming approaches generally include use of procedures (e.g.routines, subroutines, methods, functions, etc.) containing a series ofcomputational steps to be carried out as part of one or more operationsto be performed on one or more data structures. Procedural programmingcan be considered as a list of operations for the CPU to perform in alinear order of execution, optionally with loops, branches, etc. Locksare a type of synchronization mechanism for enforcing limits on accessto a resource in an environment where there are many threads ofexecution. A lock enforces a mutual exclusion concurrency controlpolicy, for example to ensure that correct results for concurrentoperations are generated as quickly as possible.

In contrast, approaches for heavily parallelized operation moretypically employ message-passing, in which multiple CPU corescommunicate over fast interconnect channels (e.g. in a same machine orbetween two or more discrete machines). In message-passing, a“requester” sends a message (which can, for example, include datastructures, segments of code, raw data, or the like) to a designatedmessage-passing worker, and the message-passing worker returns a message(which can, for example, include an operated-on data structure, segmentof code, raw data, or the like). Processes can be synchronized in thismanner, for example by requiring that a process wait for receipt of amessage before proceeding. The code for processing a single message in amessage-passing arrangement is generally lock-free and uses a veryshallow stack. A lock-free algorithm (also referred to as a non-blockingalgorithm) ensures that threads competing for a shared resource do nothave their execution indefinitely postponed by mutual exclusion.

Generally speaking, a stack is a section of memory used for temporarystorage of information. Message-passing approaches generally providesuperior performance to procedural code, for example because data areproperly partitioned and no additional synchronization besides messagequeues is generally required. Message-passing operations can beperformed by a message-passing worker, which, as used herein, isintended to refer to a type of thread or other operator for performing aset of instructions that implement a message-passing approach.

SUMMARY

In one aspect, algorithms using message-passing and algorithms usingprocedural coding approaches can coexist in a single system or group ofsystems implementing features of a data management framework. In someexamples, logical cores of the physical processor cores available withinthe system or group of systems can be divided between designation asmessage-passing workers or for execution of procedural code. Databaseobjects can be assigned to one message-passing worker such that anyoperations to be performed on the database object are executed by thelogical core designated to the message-passing worker to which thedatabase object is assigned.

In another aspect, exclusive write access to a database object of aplurality of database objects is provided via a message-passing workerof a plurality of message-passing workers to which the database objectis assigned. Read-only access is provided to any database object of theplurality of database objects via any of a plurality of job workers thatimplement procedural code. Operations can be executed by themessage-passing worker in an order in which request messages arereceived in a message queue of the message-passing worker.

Implementations of the current subject matter can include, but are notlimited to, methods consistent with the descriptions provided herein aswell as articles that comprise a tangibly embodied machine-readablemedium operable to cause one or more machines (e.g., computers, etc.) toresult in operations implementing one or more of the described features.Similarly, computer systems are also described that may include one ormore processors and one or more memories coupled to the one or moreprocessors. A memory, which can include a computer-readable storagemedium, may include, encode, store, or the like one or more programsthat cause one or more processors to perform one or more of theoperations described herein. Computer implemented methods consistentwith one or more implementations of the current subject matter can beimplemented by one or more data processors residing in a singlecomputing system or multiple computing systems. Such multiple computingsystems can be connected and can exchange data and/or commands or otherinstructions or the like via one or more connections, including but notlimited to a connection over a network (e.g. the Internet, a wirelesswide area network, a local area network, a wide area network, a wirednetwork, or the like), via a direct connection between one or more ofthe multiple computing systems, etc.

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims. While certain features of the currently disclosed subject matterare described for illustrative purposes in relation to an enterpriseresource software system or other business software solution orarchitecture, it should be readily understood that such features are notintended to be limiting. The claims that follow this disclosure areintended to define the scope of the protected subject matter.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations. In thedrawings,

FIG. 1 shows a diagram illustrating features of a database managementsystem architecture consistent with at least some implementations of thecurrent subject matter;

FIG. 2 shows a process flow chart illustrating features of a methodconsistent with implementations of the current subject matter;

FIG. 3 shows a diagram illustrating an example of handling of operationsby message-passing workers and procedural code job consistent with atleast some implementations of the current subject matter;

FIG. 4 shows a process flow chart illustrating features of a methodconsistent with implementations of the current subject matter;

FIG. 5 shows a chart illustrating a comparison of processor performanceusing mutual exclusion and message-passing approaches based on number ofoperations performed and processor cycle consumption; and

FIG. 6 shows a chart illustrating a comparison of processor performanceusing mutual exclusion and message-passing approaches based on a numberof operations performed per physical processor core.

When practical, similar reference numbers denote similar structures,features, or elements.

DETAILED DESCRIPTION

Use of message-passing for at least for some operation types in dataprocessing applications can be desirable. Use of message-passing for alloperations in a complicated database management framework may not beimmediately possible, in particular in cases whether a large amount oflegacy code would need to be rewritten to implant such an approach.However, proper resource distribution can be a non-trivial concern insystems or groups of interconnected systems in which both proceduralcoding approaches and message-passing approaches are used. For example,assigning or reserving one or more physical processor cores for use inimplementing a message-passing worker can require that those physicalprocessor cores be made unavailable for other processing tasks.Accordingly, performance of procedural code, in particular parallelizedprocedural code executing concurrently, can be negatively affected.

Implementations of the current subject matter describe techniques,methods, systems, articles or manufacture, and the like that can allowprocedural approaches and message-passing approaches to coexist onmodern computing architectures while maintaining satisfactory resourcedistribution. For example, some modern computer processors (e.g. centralprocessing units or the like) are capable of simultaneousmulti-threading (SMT) operations, which is also referred to ashyper-threading. Using SMT, for each available physical processor core,the operating system addresses two or more virtual or logical cores, andshares the workload between them when possible. Two or more threadsbeing executed by the two or more virtual or logical cores sharing thephysical processor core's resources, but each of the virtual or logicalcores has its own registers. Registers are not a part of a stack, butrather an internal state of the CPU. A program uses the stack to storespilled-out CPU registers if there are not sufficient registersavailable and to store registers of the caller routine.

Registers are used by the physical processor core when it runs aparticular thread. When processing is switched between a first threadand s second thread (for example by a program, operating system, etc.,the current values of a thread's register is saved into an area ofsystem memory specific to the first thread. Values in any previouslysaved register for the second can be loaded prior to running of thesecond thread in a context switch. Simultaneous multi-threading canimprove performance of a physical processor core in certain situations,for example by facilitating use of resources for other operations when afirst thread is currently stalled or not making full use of theavailable resources of the physical processor core. An advantageprovided by SMT is to decrease the number of dependent instructions onthe pipeline, for example through use of superscalar architectures whichenable multiple instructions to operate on separate data in parallel.The two or more logical cores can appear to an operating system orapplication as two or more processors, so the operating system orapplication can schedule two or more processes at once. In addition twoor more processes can use the same resources. If one process fails thenthe resources can be readily re-allocated. In some examples, aperformance improvement of as much as 10-30% relative to a comparablephysical processor core not using SMT is generally achievable dependingon the nature of the operations being performed by the physicalprocessor core.

Consistent with implementations of the current subject matter, at leastsome of the logical cores provided by a physical processor core aredesignated or assigned for running message-passing workers while theremaining logical cores are designated for running executable code. Inan example, a SMT-capable physical processor core supports two logicalcores. Other examples with more than two logical cores per physicalprocessor core are also with the scope of the current subject matter. Afirst logical core of a physical processor core can be designated foruse by a message-passing worker while another logical core of thatphysical processor core can be designated for execution of proceduralcode. A message queue and a set of database objects are associated witha particular message-passing worker. In other words, a message queue andset of database objects are designated to be processed by a specificmessage-passing worker. Any operation needed for a specific databaseobject is designated for execution by (and, for example, delivered to)the associated message-passing worker. Using such an approach, even aprocessing workload that is heavily skewed to either message-passingoperations or to procedural code-based operation can typically lose nomore than 9-24% performance against using all logical cores for a singletype of workload. In case the CPU core supports more than two parallelthreads, a different logical core assignment scheme is possible, basedon expected processing workload distributions.

FIG. 1 shows a diagram 100 illustrating features of a computing system102 that includes multiple physical processor cores 104A-C. While thecomputing system 102 is shown as a single, co-located system withmultiple physical processor cores, distributed architectures orcomputing frameworks in which multiple systems each having one or morephysical processor cores are linked or otherwise in communication arealso within the scope of the current subject matter. The computingsystem 102 can be accessible by one or more client machines 108A-D,either via a direct connection, a local terminal, or over a network 110(e.g. a local area network, a wide area network, a wireless network, theInternet, or the like).

A repository (e.g., a database such as a relational database) 112accessed by or maintained within the computing system 102 can store anykind of data, potentially including but not limited to definitions ofbusiness scenarios, business processes, and one or more businessconfigurations as well as transactional data, metadata, master data,etc. relating to instances or definitions of the business scenarios,business processes, and one or more business configurations, and/orconcrete instances of data objects and/or business objects that arerelevant to a specific instance of a business scenario or a businessprocess, and the like. Tables of the database or ranges within tablescan be assigned to different database partitions that are assigned todifferent hosts, for example data distribution and/or scalabilityreasons. Such a configuration can be used for large, on-premise orstand-alone systems with high performance requirements. Each physicalprocessor core 104A-C can support two (or optionally more) logical cores114A-F, which can share resources 116A-C of the physical core. Asdiscussed above, the logical cores 114A-F of each physical processorcore 104A-C can be divided between executing message-passing workers118A-C and executing procedural algorithms 120A-C. The repositoryincludes database objects 122A-G, which can include, but are not limitedto tables, parts of tables, data objects, business objects, userinterface objects, indexes, stored procedures, sequences, views, orother types of data structures for holding or reviewing data. Eachdatabase object 122A-G is assigned to a specific message-passing workerof the message-passing workers 118A-C supported on the various physicalprocessor cores 104A-C of the computing system 102.

Consistent with a first aspect of the current subject matter, an exampleof which is illustrated in FIG. 1, a method as illustrated in theprocess flow chart 200 of FIG. 2 can include the use of physicalprocessor cores capable of supporting simultaneous multi-threading,which is also referred to as hyper threading. At 202, a first logicalcore of a plurality of logical cores supported on each of a plurality ofphysical processor cores in a computing system is designated forexecution of a message-passing worker of a plurality of message workers,and at 204, a second logical core of the plurality of logical coressupported on each of the plurality of physical processor cores isdesignated for execution of procedural code such that resources of arespective physical processor core supporting the first logical core andthe second logical core are shared between the first logical core andthe second logical core. At 206, a database object in a repository isassigned to one message-passing worker of the plurality ofmessage-passing workers. At 210, an operation for execution on thedatabase object is delivered to the one message-passing worker, while at212 other, procedurally coded operations are processed using the secondlogical core on one or more of the plurality of physical processorcores. A plurality of database objects that includes the database objectreferenced at 206 can be assigned to the one message-passing worker, andeach of the plurality of database objects can have its own registermaintained by the message-passing worker to which the database object isassigned.

Approaches such as those described above can allow concurrent use in onedatabase kernel of lock-based data operations as well as parallelizedmessage-passing operations, and thereby improve the overall performanceof a computing system implementing a database management system.Currently available approaches can support either lock-based ormessage-passing operations individually, but not in the same kernel. Insome examples, table operations, which can generally be performed usinga data manipulation language (DML), can be handled via message-passingworkers. While significant improvements in parallel processing arepossible with this approach, legacy database management systems withmillions or more lines of procedural code are not readily converted.Implementations of the current subject matter can advantageously allowuse of the more efficient parallel processing possible withmessage-passing while still supporting those parts of the code that arewritten procedurally. Procedural code can be heavily stream oriented.For example, data can be loaded from main memory so that a processingstream can be built from it. Such operations are typically less memoryintensive, but do require significant processing resources. In contrast,DML operations can be more typically characterized as random accessoperations, for example in which access to discrete, separate parts ofthe memory are required (e.g., in writing a data dictionary). Theefficiency of such operations can be largely drive by cache misses(e.g., if data needed for an operation are missing from the processorcache and therefore need to be loaded from main memory). However, DMLoperations may not require as much processor resources or bandwidth.Accordingly, sharing of the physical processor core resources betweenmessage-passing operations and procedural code execution as describedherein can be advantageous.

In another aspect of the current subject matter, database objects can bemapped to message-passing workers for facilitating data access in amixed-mode environment in which message-passing and mutualexclusion-based approaches (e.g. procedural coding) are usedconcurrently within a same database kernel.

As noted above, available logical cores in the computing system 102(which can optionally include more than one discrete system) can bepartitioned for use by message-passing workers and procedural code.Internal structures of a database object can be implemented as versionedobjects, for example as described in co-pending U.S. application Ser.No. 13/770,901, filed Feb. 19, 2013 and entitled “Lock-free, ScalableRead Access to Shared Data Structures Using Garbage Collection,” thedisclosure of which is incorporated by reference herein in its entirety.

Consistent with implementations of the current subject matter, eachdatabase object (such as a table, part of a table, one or more tablecolumns, other data structures, or the like) is assigned to a specificmessage-passing worker. Advantageously, this assignment remains fixedfor a significant part of the database object's existence. The assigningof a database object to a specific message-passing worker also bindsthat database object to a single physical processor core and thereby canallow less re-reading of cached data. In cases in which a databaseobject is being frequently operated upon, the chances of the cached databeing re-usable are increased when the same physical processor corehandles all operations for a given database object.

Operations modifying the database object can be posted into the messagequeue of the message-passing worker to which the database object isassigned. The operations in the message queue can then be performedsequentially by the assigned message-passing worker. Operations readingthe database object can be executed directly by procedural code. Dataconsistency can be ensured using versioned objects and multi-versionconcurrency control (MVCC) to filter rows visible to a transaction. Inthis manner 100% scalability for the reader can be ensured.

Versioning of data objects, table control structures used by readers,etc. can include disallowing readers from acquiring locks on a datastructure. Instead, a reader works with a current version of a datastructure until a query or query plan operator ends. With thisarrangement, old versions only remain for a short period of time (e.g.,sub-seconds). As versioned objects are typically small, memory overheadis also small. In addition, even with OLTP systems, incompatible changesare rare (i.e., there are not many concurrent versions, etc.).

MVCC ensures transaction isolation and consistent reading. Each row of adatabase table can be associated with a unique, monotonically-increasingidentifier (RowID). When a new version of the record is created, thisnew version can also become a new RowID. The old version of the recordcan also be kept for parallel readers and can be cleaned (e.g. markedfor deletion) during garbage collection after a commit operation.Certain operations, like locking using embedded MVCC information, can beexecuted directly in a reader.

FIG. 3 shows a diagram 300 illustrating some features consistent withimplementations of the current subject matter. Two message-passingworkers 302, 304 are shown. As discussed above are supported on separatelogical cores of physical processor cores of a computing system. Eachmessage-passing worker 302, 304 has a message queue 306, 310. Alsoincluded in FIG. 3 are two job workers 312, 314, which can be supportedon different separate logical cores than the message-passing workers302, 304. Messages can be directed to a message queue 306 or 310 of amessage-passing worker 302 or 304 by other message-passing workers or byjob workers indicated by the dashed lines.

Each message-passing worker 302 or 304 can have exclusive write accessto a set of database objects as designated by the solid arrows. Forexample, the first message-passing worker 302 can have exclusive writeaccess to a first table (T₁), a first column in the first table (T₁C₁),and a second column in a second table (T₂C₂) while the secondmessage-passing worker can have exclusive write access to a second table(T₂), a first column in the second table (T₂C₁), and a second column inthe first table (T₁C₂). Overlap of data objects is possible as shown inFIG. 3 in that write access to a table can be available from onemessage-worker while write access to a column within that table can beavailable from another message-worker. The job workers 312, 314 can haveread-only access to any of the data objects via versioned structures asindicated by the dotted lines. This read-only access can be via a dirtyread with no locks, for example with data consistency ensured usingversioned objects and multi-version concurrency control to filtervisible rows.

FIG. 4 shows a process flow chart 400 illustrating features of a methodconsistent with implementations of the current subject matter. At 402,each of a plurality of database objects in a database management systemis assigned to a specific message-passing worker of a plurality ofmessage-passing workers. Each of the plurality of message-passingworkers executes on a first logical core that shares with at least asecond logical core one or more resources of a physical processor coreof a plurality of physical processor cores. The second logical coreexecutes a job worker of a plurality of job workers that implementprocedural code. In other words, as discussed above, the physicalprocessor cores of the computing system or systems each support SMT suchthat two or more logical cores share resources of each physicalprocessor core. A first logical core of each physical processor coresupports a message-passing worker and a second logical core of eachphysical processor core support a job worker that implements proceduralcode.

At 404, exclusive write access to a database object of the plurality ofdatabase objects is provided via a message-passing worker of theplurality of message-passing workers to which the database object isassigned. Read-only access to any database object of the plurality ofdatabase objects is provided via any of the plurality of job workers at406. At 410, operations are executed by the message-passing worker in anorder in which request messages are received in a message queue of themessage-passing worker. In this manner, locking is not required tomaintain exclusivity of write access to a database object, because allwrite operations on the database object occur via a singlemessage-passing worker, and the worker performs requested operationssequentially according to its message queue.

Database objects can be assigned to specific message-passing worker in arandom or round-robin fashion. Performance statistics can be maintainedand monitored for each database object (such as, for example, one ormore of access frequency, processor time spent, etc.) and each queue(such as, for example, queue length, etc.). A rebalancing operation canrun periodically to reassign database objects for equalizing the load onindividual message-passing workers. Various approaches to rebalancingcan be applied. After rebalancing, it is possible that a message-passingworker may receive a request for an operation on a database object thatis no longer assigned to the message-passing worker. In such a case, thereceiving message-passing worker can post the request message into aproper message queue of a second message-passing worker that to whichthe database object is now assigned new owner (e.g. via a forwardingoperation).

With a message-passing approach such as is described herein, in which agiven database object can be assigned to a single message-passing workerthat consistently effectively serializes operations on a single databaseobject, locking of internal structures is not necessary to maintainconcurrency. Furthermore, since a database object is accessed only froma single thread on a single logical core, improved data locality isprovided, for example because the database object can be easily kept inphysical processor-local memory in a non-uniform memory access system.Also, a hit rate for cached data can be improved. While procedural coderunning in parallel and handling other objects may degrade cacheperformance for message-passing workers, the overall effect is a netpositive for many examples of typical database management system usecases.

In general, processing a same amount of operations using message-passingtechnique requires much less CPU time in total than processing themusing parallel threads competing for a lock (depending on systemconfiguration, up to order of magnitude). FIG. 5 and FIG. 6 show charts500, 600 illustrating features of mutual exclusion and message-passingapproaches consistent with locking algorithms typically used inprocedural coding for database operations.

As shown in the chart 500 of FIG. 5, the number of operations per secondthat can be performed by a physical processor core using message-passing(as shown by the first line 502 connecting the triangle icons) peaks ata relatively low number of total threads and then drops off while amutual exclusion approach (as shown by the second line 504 connectingthe diamond icons) shows less decline in performance with increasednumber of threads. However, the mutual exclusion approach results in aprogressively increasing amount of processor cycle usage (as shown bythe third line 506 connecting the square icons) with increasing numberof threads while processor cycle usage for the message-passing approach(as shown by the fourth line 510 connecting the diamond icons) is mostlyunchanged by the thread count. FIG. 6 shows a chart 600 comparing anamount of useful work that can be accomplished by the two approaches asa function of thread count. As shown in FIG. 6, the number of operationsper second per physical processor core achievable by message processing(as shown by the solid bars 602A-F) is much greater overall anddecreases less significantly with increasing numbers of threads than themutual exclusion approach (as shown by the hashed bars 604A-F).

The measurement results represented in the charts 500, 600 of FIG. 5 andFIG. 6, respectively, reflect the effect of the two approaches on largenumbers of relatively simple operations, such as for example a simpleincrement or the like. For a smaller number of more complex,long-running operations, the performance benefits will still occur butmay be less pronounced. The approach discussed herein with regards tothe use of message passing workers can generally result in improvementsto the processing efficiency of smaller operations (such as for examplesingle DML operations), which are more complex than simple incrementoperations, but are nonetheless fairly fast in terms of CPU consumption.The benefits of the approaches described herein are thereforesignificant.

One or more aspects or features of the subject matter described hereincan be realized in digital electronic circuitry, integrated circuitry,specially designed application specific integrated circuits (ASICs),field programmable gate arrays (FPGAs) computer hardware, firmware,software, and/or combinations thereof. These various aspects or featurescan include implementation in one or more computer programs that areexecutable and/or interpretable on a programmable system including atleast one programmable processor, which can be special or generalpurpose, coupled to receive data and instructions from, and to transmitdata and instructions to, a storage system, at least one input device,and at least one output device. The programmable system or computingsystem may include clients and servers. A client and server aregenerally remote from each other and typically interact through acommunication network. The relationship of client and server arises byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

These computer programs, which can also be referred to programs,software, software applications, applications, components, or code,include machine instructions for a programmable processor, and can beimplemented in a high-level procedural language, an object-orientedprogramming language, a functional programming language, a logicalprogramming language, and/or in assembly/machine language. As usedherein, the term “machine-readable medium” refers to any computerprogram product, apparatus and/or device, such as for example magneticdiscs, optical disks, memory, and Programmable Logic Devices (PLDs),used to provide machine instructions and/or data to a programmableprocessor, including a machine-readable medium that receives machineinstructions as a machine-readable signal. The term “machine-readablesignal” refers to any signal used to provide machine instructions and/ordata to a programmable processor. The machine-readable medium can storesuch machine instructions non-transitorily, such as for example as woulda non-transient solid-state memory or a magnetic hard drive or anyequivalent storage medium. The machine-readable medium can alternativelyor additionally store such machine instructions in a transient manner,such as for example as would a processor cache or other random accessmemory associated with one or more physical processor cores.

To provide for interaction with a user, one or more aspects or featuresof the subject matter described herein can be implemented on a computerhaving a display device, such as for example a cathode ray tube (CRT) ora liquid crystal display (LCD) or a light emitting diode (LED) monitorfor displaying information to the user and a keyboard and a pointingdevice, such as for example a mouse or a trackball, by which the usermay provide input to the computer. Other kinds of devices can be used toprovide for interaction with a user as well. For example, feedbackprovided to the user can be any form of sensory feedback, such as forexample visual feedback, auditory feedback, or tactile feedback; andinput from the user may be received in any form, including, but notlimited to, acoustic, speech, or tactile input. Other possible inputdevices include, but are not limited to, touch screens or othertouch-sensitive devices such as single or multi-point resistive orcapacitive trackpads, voice recognition hardware and software, opticalscanners, optical pointers, digital image capture devices and associatedinterpretation software, and the like.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and subcombinations of the disclosed featuresand/or combinations and subcombinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A system comprising: at least one programmableprocessor comprising at least one physical core and a plurality oflogical cores; and at least one memory comprising instructions which,when executed by the at least one programmable processor, causeoperations comprising: designating, for use by a first message-passingworker of a plurality of message-passing workers, a first logical corefrom the plurality of logical cores; assigning, to the firstmessage-passing worker, a first set of database objects from a pluralityof database objects in a database management system, the firstmessage-passing worker having write access to the first set of databaseobjects; assigning, to a second message-passing worker of the pluralityof message-passing workers, a second set of database objects from theplurality of database objects, the second message-passing worker havingwrite access to the second set of database objects, wherein the firstmessage-passing worker and the second message-passing worker havesimultaneous write access to at least one database object common to thefirst and second set of database objects; wherein the database objectsare mapped to the first and second message-passing workers forfacilitating data access in a mixed-mode environment in whichmessage-passing and procedural coding approaches are used concurrentlywithin a same database kernel; providing, via a job worker, read-onlyaccess to at least a portion of the plurality of database objects,wherein the read-only access executed via a dirty read with no locks toensure data consistency using versioned objects and multi-versionconcurrency control to filter visible rows; designating, for use by thejob worker, a second logical core from the plurality of logical cores,the first and second logical cores sharing one or more resources of theat least one physical core; and directing, via the job worker, aplurality of messages to a message queue of at least one of the firstand second message-passing worker.
 2. The system as in claim 1, whereinthe first set of database objects comprises a database table, whereinthe second set of database objects comprises a column in the databasetable, and wherein the first and second message-passing workersconfigured to modify a database object in the column of databaseobjects.
 3. The system as in claim 1, wherein the operations furthercomprise: executing, by the first and second message-passing worker,operations on the first and second set of database objects, wherein theexecuting is based on an order of received requests in a message queueof the first message-passing worker.
 4. The system as in claim 1,wherein the operations further comprise: reassigning the plurality ofdatabase objects to equalize a load across the plurality ofmessage-passing workers.
 5. The system as in claim 4, wherein theoperations further comprise: receiving, by a rebalanced message-passingworker of the plurality of message-passing workers after thereassigning, a request message pertaining to a reassigned databaseobject of the plurality of database objects, the reassigned databaseobject formerly assigned to the rebalanced message-passing worker andcurrently assigned to a new message-passing worker of the plurality ofmessage-passing workers; and posting, by the rebalanced message-passingworker, the new request message into a message queue of the newmessage-passing worker.
 6. The system as in claim 1, wherein theassigning to the first message-passing worker comprises at least one ofa round-robin assignment of the plurality of database objects to theplurality of message-passing workers or a random assignment of theplurality of database objects to the plurality of message-passingworkers.
 7. The system as in claim 4, wherein the operations furthercomprise: maintaining and monitoring performance statistics for eachdatabase object of the plurality of database objects, wherein thereassigning is performed in response to the maintaining and monitoring.8. A computer program product comprising a non-transitorymachine-readable medium storing instructions that, when executed by atleast one programmable processor, causes operations comprising:designating, for use by a first message-passing worker of a plurality ofmessage-passing workers, a first logical core from a plurality oflogical cores; assigning, to the first message-passing worker, a firstset of database objects from a plurality of database objects in adatabase management system, the first message-passing worker havingwrite access to the first set of database objects; assigning, to asecond message-passing worker of the plurality of message-passingworkers, a second set of database objects from the plurality of databaseobjects, the second message-passing worker having write access to thesecond set of database objects, wherein the first message-passing workerand the second message-passing worker have simultaneous write access toat least one database object common to the first and second set ofdatabase objects; wherein the database objects are mapped to the firstand second message-passing workers for facilitating data access in amixed-mode environment in which message-passing and procedural codingapproaches are used concurrently within a same database kernel:providing, via a job worker, read-only access to at least a portion ofthe plurality of database objects, wherein the read-only access executedvia a dirty read with no locks to ensure data consistency usingversioned objects and multi-version concurrency control to filtervisible rows; designating, for use by the job worker, a second logicalcore from the plurality of logical cores, the first and second logicalcores sharing one or more resources of the at least one physical core;and directing, via the job worker, a plurality of messages to a messagequeue of at least one of the first and second message-passing worker. 9.The computer program product as in claim 8, wherein the first set ofdatabase objects comprises a database table, wherein the second set ofdatabase objects comprises a column in the database table, and whereinthe first and second message-passing workers configured to modify adatabase object in the column of database objects.
 10. The computerprogram product as in claim 8, wherein the operations further comprise:executing, by the first and second message-passing worker, operations onthe first and second set of database objects, wherein the executing isbased on an order of received requests in a message queue of the firstmessage-passing worker.
 11. The computer program product as in claim 8,the operations further comprise: reassigning the plurality of databaseobjects to equalize a load across the plurality of message-passingworkers.
 12. The computer program product as in claim 11, wherein theoperations further comprise: receiving, by a rebalanced message-passingworker of the plurality of message-passing workers after thereassigning, a request message pertaining to a reassigned databaseobject of the plurality of database objects, the reassigned databaseobject formerly assigned to the rebalanced message-passing worker andcurrently assigned to a new message-passing worker of the plurality ofmessage-passing workers; and posting, by the rebalanced message-passingworker, the new request message into a message queue of the newmessage-passing worker.
 13. A computer-implemented method comprising:designating, for use by a first message-passing worker of a plurality ofmessage-passing workers, a first logical core from the plurality oflogical cores; assigning, to the first message-passing worker, a firstset of database objects from a plurality of database objects in adatabase management system, the first message-passing worker havingwrite access to the first set of database objects; assigning, to asecond message-passing worker of the plurality of message-passingworkers, a second set of database objects from the plurality of databaseobjects, the second message-passing worker having write access to thesecond set of database objects, wherein the first message-passing workerand the second message-passing worker have simultaneous write access toat least one database object common to the first and second set ofdatabase objects; wherein the database objects are mapped to the firstand second message-passing workers for facilitating data access in amixed-mode environment in which message-passing and procedural codingapproaches are used concurrently within a same database kernel;providing, via a job worker, read-only access to at least a portion ofthe plurality of database objects, wherein the read-only access executedvia a dirty read with no locks to ensure data consistency usingversioned objects and multi-version concurrency control to filtervisible rows; designating, for use by the job worker, a second logicalcore from the plurality of logical cores, the first and second logicalcores sharing one or more resources of the at least one physical core;and directing, via the job worker, a plurality of messages to a messagequeue of at least one of the first and second message-passing worker.14. The computer-implemented method as in claim 13, wherein the firstset of database objects comprises a database table, wherein the secondset of database objects comprises a column in the database table, andwherein the first and second message-passing workers configured tomodify a database object in the column of database objects.
 15. Thecomputer-implemented method as in claim 13, wherein the operationsfurther comprise: executing, by the first and second message-passingworker, operations on the first and second set of database objects,wherein the executing is based on an order of received requests in amessage queue of the first message-passing worker.
 16. Thecomputer-implemented method as in claim 13, wherein the operationsfurther comprise: reassigning the plurality of database objects toequalize a load across the plurality of message-passing workers.
 17. Thecomputer-implemented method as in claim 16, wherein the operationsfurther comprise: receiving, by a rebalanced message-passing worker ofthe plurality of message-passing workers after the reassigning, arequest message pertaining to a reassigned database object of theplurality of database objects, the reassigned database object formerlyassigned to the rebalanced message-passing worker and currently assignedto a new message-passing worker of the plurality of message-passingworkers; and posting, by the rebalanced message-passing worker, the newrequest message into a message queue of the new message-passing worker.